A Japanese facial gesture, usually considered childish. It consists of pulling down one lower eyelid to show the red inside, while sticking the tongue out. It is sometimes accompanied by the sound べえだ (beeda, pronounced "behhh-dah"). This gesture is also done in France and Québec, where it is accompanied by saying "mon oeil" ("my eye").
The gist of the the gesture is an infantile taunt - the Japanese equivalent of thumbing your nose at someone, and/or yelling "Nyah nyah nyah" or "Neener neener" or the like.